Would tolls keep SR 520 traffic out of the Arboretum?

Published 10:00 pm, Wednesday, December 1, 2010

People looking for a shortcut to neighborhoods south of the new State Route 520 Bridge could someday be in for a surprise: Tolls on the scenic drive through Washington Park Arboretum.

Making people pay to use the Arboretum as a side route from the bridge is among several options that a 520 workgroup is recommending to be studied as part of a broader traffic management plan. Other options include limits on traffic during certain times of day and restricting turns or modifying signal timing at key intersections.

With final planning on the $4.6 billion bridge underway, officials are brainstorming how best to reduce traffic that cuts through the Arboretum from the highway.

About 18,000 vehicle trips are made every day on Lake Washington Boulevard East, a narrow, two-lane road. A majority of that traffic is headed for access ramps from the boulevard to the 520 Bridge. That's much more traffic and noise than Arboretum stewards would like to see along the historic Olmstead boulevard, which was designed as a pleasurable drive connecting Seattle's scenic parks.

The state's preferred design alternative for the new bridge would remove the on- and off-ramps between the Arboretum and the bridge. While most traffic would enter and exit from a new Montlake interchange, a new exit-only ramp would be connected to a new extension of 24th Avenue East on a lid over the highway. Traffic from there would be funneled to a new signalized intersection at East Lake Washington Boulevard, giving drivers a choice to turn right toward Montlake Boulevard and 24th Avenue, or to turn left toward the Arboretum.

Miller said she is pleased the state agreed to remove the existing highway ramps in the Arboretum. But population growth is expected to add another 2,000 vehicle trips per day through the area by 2030, which runs strongly counter to Miller's desire to see traffic reduced from 18,000 to 4,000 vehicles per day.

Earlier this year, the state Legislature created a workgroup to refine the state's preferred 520 bridge design and make recommendations by Dec. 31. This week, the group, which includes the state and city transportation departments, transit agencies, the University of Washington and the arboretum, unveiled recommendations for managing traffic through the Arboretum and for funding transit improvements that will be critical through the 520 corridor. Public comments will be accepted through Dec. 15. Their reports can be viewed here.

For a majority of the traffic coming from areas south of 520, the main feeder route is 23rd Avenue East, a four-lane arterial that turns into 24th Avenue before changing again into Montlake.

While the new 520 bridge will be wider -- four general-purpose lanes and two HOV lanes -- it is not expected to add more traffic to the Arboretum. The problem is the traffic that's already there and population growth, officials say.

Electronic and photo tolling is set to start next spring on the bridge, with a proposed toll rate of up to $3.50 for peak commuters across Lake Washington. Miller wonders whether the same system of transponders could be used in the Arboretum, so a driver who exits from the bridge and drives through the Arboretum would be charged an extra fee.

Local traffic and drivers visiting the Arboretum who aren't passing through from the highway wouldn't be tolled, she said.

A new floating bridge across Lake Washington is expected to open in 2014. The westside segment, from the bridge landing to I-5, likely wouldn't be completed until sometime after due to funding shortfalls.

State and city officials likely wouldn't begin studying the issue of tolling until 2012.

"Technically, you could make anything happen. But does it have the desired effect? Are you setting yourself up for a rate that never discourages people to drive through the Arboretum? Or would the infrastructure be so expensive that it would never pay it down?"

Both the state Legislature and the City Council likely would have to approve. The City Council has the authority to toll streets through a Transportation Benefits District, although it's unclear whether it would be used here.

State Route 520 commuters are encouraged to purchase electronic "Good 2 Go" transponders that deduct tolls from prepaid accounts. A possible question is whether an Arboretum toll could be collected as part of the 520 program.

Another challenge is that pushing more traffic out of the Arboretum could create undesirable consequences at the Montlake interchange and on 23rd Avenue, where close to 20,000 vehicles now travel every day.

"That's the most critical issue," Wieland said. "Traffic isn't just going to disappear. It will go somewhere. And while true that 24th Avenue (which turns into 23rd) is an arterial, it's also a really high-use transit corridor … and part of what we have to do is make sure transit speed and reliability are still maintained."

In the meantime, the state is preparing a range of immediate "traffic calming measures" in the Arboretum, including more marked crosswalks, speed cushions and other safety devices to slow traffic for bicyclists and pedestrians.

WSDOT has chipped in $200,000 to pay for the improvements, which include a new marked crosswalk and signs on Arboretum Drive and a raised crosswalk just north of Interlaken Avenue. That work will start in April 2011.

Landscaped curb bulbs and new striping will be installed where Lake Washington Boulevard intersects Foster Island Road and the on-ramp to the 520 Bridge. Radar speeds signs also may be installed to encourage drivers to slow down.

"There are always some folks who don't like traffic-calming devices. But the big benefit is, it changes people's sense of safety," said Wieland,who has been involved with the workgroup.

WSDOT is paying for the improvements because the new bridge will better connect bicyclists and pedestrians to the Arboretum, she said. That includes a new lid over the highway with a network of trails that will link to the Arboretum.

About 90 percent of traffic that uses the existing Arboretum ramps is from neighborhoods surrounding it. About 50 percent of morning traffic headed east across Lake Washington from those ramps originates south of Madison Park. About 25 percent comes from Madison Park, according to the workgroup materials.

Other potential traffic management options include lengthening the left-turn signal from eastbound East Madison Street onto 23rd Avenue. There are concerns that the signal is too short, encouraging more drivers to head straight and turn left further up the road onto Lake Washington Boulevard.

There also could be restrictions at the new intersection of 24th Avenue and East Lake Washington Boulevard after the bridge is built.

City Councilwoman Sally Bagshaw, chair of the parks committee, said she'd like to see how some of the smaller steps improve traffic before considering tolls. But she's open to exploring all recommendations.

"I think slowing traffic down through the Arboretum and reducing noise and making it a more pedestrian-friendly place to be is a really positive step in the right direction," she said.

"So much traffic is going through there. It really has become almost a highway," she said.